Genetics help hound health

May 21, 2004By Helen R. PilcherThis article courtesy of Nature News.

DNA test maps evolution of dog breeds.

Does your mutt look more mastiff than mongrel? Then geneticists are on hand to help prove your pooch's parentage. Researchers have developed a DNA test that can unravel any dog's ancestry, and pinpoint its pedigree with over 99% accuracy.

"It could help mutt owners work out what breeds are hidden in their dog," says Elaine Ostrander from the Fred Hutchinson Cancer Research Centre, Seattle, who co-developed the test.

As well as satisfying owners' curiosity, the test could help dogs' health. There are over 350 inherited disorders in the purebred dog population. German shepherds, for example, commonly suffer hip displacement. Golden retrievers often develop cancer of the white blood cells.

Knowing that your dog has a genetic predisposition to a particular condition means you can take preventative measures, says Ostrander. Mutts that are part German shepherd could be given a diet that promotes muscular development. Owners of cancer-prone dogs could keep watch for early symptoms.

The test may also help owners of Staffordshire bull terriers, says Jeff Sampson, coordinator of the Canine Genetics Centre at the UK's Kennel Club. These dogs are commonly mistaken for more aggressive pit bull terriers, which means that, in the UK, owners can find themselves on the wrong side of the Dangerous Dogs Act. This 1991 legislation makes it illegal to own a pit bull without special dispensation from a court. A test would help prevent confusion, says Sampson.

Tess of the Baskervilles

Ostrander's team analysed the genetic makeup of 414 dogs, from 85 different breeds, including that of her own purebred border collie, Tess. They pulled out 96 landmark regions from the dogs' DNA, which showed clear differences between each breed. "This tells us that dog breeds are real," says Ostrander.

The study, reported in Science1, also sheds light on the evolution of dog breeds. Over 400 different breeds have been described, of which 152 are recognized by the American Kennel Club. The researchers used their results to construct a family tree for dogs and their ancestor, the wolf.

Although most breeds emerged in Europe during the past several hundred years, some came from Asia or Africa at least 2000 years ago, the study reveals: the saggy-faced Shar-Pei and the pint-sized Pekingese were among the early developers.

Surprisingly, some breeds thought to have originated long ago turn out to be fresh-faced impostors. The Pharaoh and Ibizan hounds of today were thought to be direct descendants of ancient Egyptian dogs, immortalized in stone on tomb walls over 5,000 years ago. Not so. Both hounds have been recently created from combinations of other breeds.

The study also reveals that, based on their genetics, modern dogs fall into three categories, loosely termed herders, hunters and guarders. Herders include collies and sheepdogs; hunters contain hounds and terriers; and guard dogs boast mastiffs and bulldogs. The groups probably arose in the 1800s when Europeans first established breed clubs.